Mr. Holder is expected to be questioned about the matter Wednesday during a hearing before the House Judiciary Committee. Committee Chairman Bob Goodlatte, Virginia Republican, said he plans to ask Mr. Holder “pointed questions” about the issue.

Members of Congress on both sides of the aisle had plenty of questions Tuesday.

Sen. Patrick J. Leahy, Vermont Democrat and Senate Judiciary Committee chairman, said he is “very troubled” by the accusations.

“The burden is always on the government when they go after private information — especially information regarding the press or its confidential sources,” he said. “I am concerned that the government may not have met that burden.”

Sen. Chuck Grassley of Iowa, the ranking Republican on the Senate Judiciary Committee, questioned whether Mr. Holder had signed off on the seizure of the AP records.

“The department’s regulations state that prosecutors should obtain the attorney general’s personal sign-off when a free press is at stake, so the Obama administration needs to be transparent with its rationale for such a sweeping intrusion and detail whether the process outlined in regulation and the U.S. attorney’s manual were followed and justified for national security,” he said.

Administration defense

U.S. Attorney Ronald C. Machen Jr. in Washington acknowledged in a letter to the AP that his office had obtained the records. His spokesman, Bill Miller, said Mr. Machen’s office takes seriously its obligations to follow all applicable laws, federal regulations and Justice Department policies when issuing subpoenas for phone records of media organizations.

“Those regulations require us to make every reasonable effort to obtain information through alternative means before even considering a subpoena for the phone records of a member of the media. We must notify the media organization in advance unless doing so would pose a substantial threat to the integrity of the investigation,” he said.

“Because we value the freedom of the press, we are always careful and deliberative in seeking to strike the right balance between the public interest in the free flow of information and the public interest in the fair and effective administration of our criminal laws,” he said.

The AP said it was notified of the seizure after the records already had been obtained. The news organization also said it held the story at the request of the administration for a time and published it only when officials told AP that national security concerns had been allayed.

The story on the foiled Yemen plot was published one day before President Obama planned to release the news publicly.

The White House on Tuesday said it had no knowledge of the investigation and referred all inquiries to the Justice Department.

“The president is a strong defender of the First Amendment,” said White House spokesman Jay Carney. “He also of course recognizes the need for the Justice Department to investigate alleged criminal activity without undue influence.”